So you booked a fare on American, Delta, United or some other airline that has economy as well as "premium" economy seating, and when you go to choose a seat the website is telling you that only the more expensive premium economy seats are available. This doesn't mean that you won't eventually get a seat assignment or a seat (if you get involuntarily bumped, that's another story, but it rarely happens). Don't cough up the extra money for a premium seat. If in fact all the "cheap" seats are taken, you'll get a premium economy seat when you check in. You can also try calling the airline directly to see if they'll give you a seat assignment.

2. Watch for (and ask for) cheap last-minute upgrades to business and first class.

The best seats on the plane, clearly, are in business and/or first class, but they sometimes cost many times what an economy seat goes for. For example, I frequently fly the LA-NYC route, where you can still (amazingly) find seats for $129 each way in coach, but business class costs $2,200 or more. However, I've been offered last-minute upgrades (when checking in online at home, at the airport kiosk or even at the gate) for as little as $250 on top of the $129 fare, a huge savings. If you're not offered a discounted upgrade, it doesn't hurt to ask when you check in.

3. Don't assume that business and first class fares cost 10 times the economy class price.

They don't always. There are often nonrefundable business and first class fares going for relatively little more than economy and often for the same price as refundable coach fares. Recently I flew from New York JFK to Boston in first class on American for $140 each way when economy class (or cattle class) on the Delta Shuttle was charging $400 from LaGuardia. I flew Los Angeles to Fort Lauderdale on a connection through Atlanta on Delta for $349 one-way in first class, not a huge premium over the economy class fare, which is sometimes $200 each way on that route. Both these deals were nonrefundable, but still.

You can see seat maps for almost all airlines and aircraft types here. All seats are not created equal, and Seat Guru will tell you which plane types, airlines and seats might have more legroom or be otherwise more desirable.

Other airlines (TWA, American) have experimented unsuccessfully with giving every seat in economy class extra leg room, but only JetBlue seems to have made a go of it. JetBlue's A320/A321 aircraft seat rows are spaced at least 33-34 inches apart in coach compared to 31-32 inches on some airlines; and JetBlue's "even more space" seats range from 37 to 41 inches apart, according to Seat Guru.

6. Use your frequent flier miles to upgrade rather than on an inexpensive economy class fare.

Everyone complains about economy class, but it's pretty easy to buy your way out with miles. I never use miles for economy class travel. Instead, I upgrade the cheapest economy class fare to business or first class using 15,000 miles each way on American and United. What is better value? Spending 25,000 points on a $250 coach fare or 15,000 miles upgrading a $139 coach fare to a $2,500 business class fare? By the way, I earn those miles by applying for airline-affiliated credit cards with those 40,000 (or more) bonus mile offers, and by never buying anything online without checking the bonus mile offers on the airlines' shopping malls. (www.airfarewatchdog.com/blog/3801194/get-bonus-frequent-flyer-miles-when-shopping-online/).

7. If you fly on United frequently, consider the Economy Plus annual subscription.

Fewer people travel on those days, so there's a bit more chance the middle seat will be open.

9. Fly on a newer plane.

Even if a plane with that "new plane smell" won't give you more legroom, at least it will have better in-flight entertainment, better power port options and other benefits.

10. Sometimes you just have to pay for an advance seat assignment on some airlines.

It's certainly not ideal, but if you're flying on an airline like British Airways, which only lets economy class passengers request specific seat assignments 24 or fewer hours before departure, it really does pay to pay up for a seat assignment. You'll find that most of your fellow passengers have done this and you'll get stuck with the worst seats on the plane if you don't follow suit. On a recent trip from Hong Kong to London on a British Airways A380 in economy my traveling companion and I paid for the two-by-two "twin" seats at the emergency exit with no one seated in front of us. The extra privacy and access made the 13-hour trip just barely bearable.